Acetylcholine is the transmitter of cholinergic system. In mitochondria the acetyl-coA combined with choline and with the help of choline acetyltransferase formed acetylcholine. Acetylcholine is destroyed by cholinesterases into choline and acetic acid. There are two type of cholinesterases, True cholinesterases which is present in cholinergic neurons, ganglia, RBCs and neuromuscular junction. Pesudocholinesterases which is presenr in plasma and liver.
There are two type of cholinergic receptor Muscarinic and nicotinic receptors. Both are G-protein couple receptor and stimulates the production of intracellular second messenger. Muscrinic receptor are further divided into 5 subtypes. M1-M5. M1 is found in Gastric glands, Autonomic ganglia, and CNS. M2 is present on heart. M3 found on smooth muscles, Exocrine gland, Endothelial cells. M4 and M5 are found CNS. Nicotinic receptors are divided into Nn and Nm found in autominc ganglia, adrenal medulla and neuromuscular junction.
Cholinergic agonist and antagonist drugs classification list are given below.
Classification of Cholinomimentics or parasympathomimetics agents:
Following is the drugs of classification of cholinergic agonists list.
cholinergic agonists is divided into Directly acting and Indirectly acting.
- Choline esters ( Mnemonics ABC )
Indirectly acting (anticholinesterases).
- Reversible (carbamates).
2. Irreversible (Organophosphorus).
- Sarin, Soman, Tabun. (nerve gases).
Anticholinergic agents ( cholinergic Receptor Blockers):
Following are the drugs antagonist list given below.
Antimuscarinic agents ( Anticholinergic agents ).
- Natural alkaloids.
- Scopolamine. ( Hyoscine ).
2. Semisynthetic and synthetic antimuscarinic agents.
- Atropine derivatives used as mydriatic. Homatropine, Cyclopentolate, tropicamide.
- Atropine derivatives used as COPD and Bronchial asthma. Ipratropium bromide, Tiotropium bromide.
- Atropine derivatives used as peptic ulcer. pirenzepine, telenzepine, clidinium, propantheline.
- Atropine derivatives used as spasmodic. dicyclomine, valethalmate, flavoxate, oxybutynin, tolterodine, darifenacin.
- Atropine derivatives used as preanaesthetic. Glycopyrrolate.
- Atropine derivatives used as parkinsonism. Benzhexol, benztropin, biperiden, procyclidine.